Colonoscopy performed on a 25 - year - old woman with eating disorder showed dark brown to black pigmentary deposit in the lining of the large intestine. Histopathology of biopsy revealed pigment laden macrophages within the lamina propria. The woman on probing revealed use of laxatives for the 9 months to lose weight. What could be the probable laxative agent that could have caused these findings?

Laxatives and purgatives causes semi solid stools and watery stools respectively. Includes:- Bulk forming : Bran,Psyllium,Ispaghula- Osmotic purgatives: Saline, lactulose, polyethylene glycol,Sodium potassium tarate- Stool softener: Docussate,Liquid Paraffin- Stimulant purgatives: * Organic : Bisacodyl, sodium pico sulfate* Anthraquinones: Senna and cascara. S/E: Melanosis coli.* Fixed oil : Castor oil As colonoscopy shows dark brown to black pigmentary deposit in the lining of large intestine, most likely dug she could be taking is senna. Bisacodyl is also implicated in causing melanosis coli.